1. Field of the Invention
The invention is related to the field of communications, and in particular, to converged charging systems and corresponding methods for converging offline charging and online charging in communication networks.
2. Statement of the Problem
The 3rd Generation Partnership Project (3GPP) standard group has defined a set of specifications about online charging systems and offline charging systems to cover charging in the various network domains (i.e., a circuit switching network domain, a packet switching network domain, or a wireless domain), IP multimedia subsystems, and emerging 3G application services. However, the online charging specification and the offline charging specification are defined in a separate way and operate in a separate manner.
FIG. 1 illustrates a charging architecture 100 as defined by the 3GPP. The charging architecture 100 may be found in the technical specification 3GPP TS 32.240. The left part of FIG. 1 illustrates the offline charging system 102 of the charging architecture 100. Offline charging system 102 includes a Charging Data Function (CDF) 110 and a Charging Gateway Function (CGF) 112. The right part of the FIG. 1 illustrates the online charging system (OCS) 104 of the charging architecture 100. The detailed functional components of online charging system 104 may be found in the technical specification 3GPP TS 32.296. Offline charging system 102 and online charging system 104 are both operable to transmit charging data records (CDR) to a billing system 106. Offline charging is generally defined as a charging mechanism where charging information does not affect, in real-time, the service rendered. Online charging is generally defined as a charging mechanism where charging information can affect, in real-time, the service rendered, and therefore a direct interaction of the charging mechanism with session/service control is needed.
Offline charging system 102 communicates with the following elements or functions to receive charging information: a circuit-switched network element (CS-NE) 121, a service network element (service-NE) 122, a SIP application server (AS) 123, Multimedia Resource Function Control (MRFC) 124, Media Gateway Control Function (MGCF) 125, Break out Gateway Control Function (BGCF) 126, Proxy-Call Session Control Function (CSCF)/Interrogate-CSCF (I-CSCF) 127, Serving-CSCF (S-CSCF) 128, Wireless LAN (WLAN) 129, SGSN 130, GGSN, 131, and Traffic Plane Function (TPF) 132. These elements and functions are known to those familiar with the 3GPP specifications. Online charging system 104 communicates with the following elements or functions to receive charging information: circuit-switched network element (CS-NE) 121, service network element (service-NE) 122, SIP application server 123, MRFC 124, S-CSCF 128, Wireless LAN (WLAN) 129, SGSN 130, GGSN, 131, and Traffic Plane Function (TPF) 132. These elements and functions are known to those familiar with the 3GPP specifications.
FIG. 2 illustrates online charging system 104 as defined by the 3GPP. Online charging system 104 includes Online Charging Functions (OCF) 202. Online charging functions 202 include Session-Based Charging Function 204 and Event-Based Charging Function 206. Online charging system 104 further includes an Account Balance Management Function (ABMF) 208, an online Rating Function (RF) 210, and a Charging Gateway Function (CGF) 212.
FIG. 3 illustrates a generalization of the charging architecture 100 as defined by the 3GPP to show the operation of the charging architecture 100. Charging architecture 100 includes a Charging Trigger Function (CTF) 302, offline charging system 102, online charging system (OCS) 104, and billing system 106. Both offline charging system 102 and online charging system (OCS) 104 introduce a charging gateway function, which are charging gateway function (CGF) 112 and charging gateway function (CGF) 212, respectively. Charging gateway function 112 and charging gateway function 212 act as a gateway between the network and the billing system 106 to provide the CDR pre-processing functionality. Offline charging system 102 includes a charging data function (CDF) 110 and charging gateway function 112. Online charging system 104 includes online charging function (OCF) 202, account balance management function (ABMF) 208, an online rating function (RF) 210, and charging gateway function 212. Billing system 106 includes offline rating function (RF) 304.
According to the 3GPP standards, the charging trigger function 302 is the focal point for collecting the information pertaining to chargeable events within a network element (not shown). The charging trigger function 302 in one or more network elements generates charging information for one or more calls. Depending on subscriber provisioned charging characteristics, a charging trigger function 302 transmits offline charging information to the charging data function 110 via Rf interface 310. A charging trigger function 302 transmits online charging information to online charging system 104 via Ro interface 311.
For offline charging, the charging data function 110 receives the offline charging information for a call or a call session. The charging data function 110 generates a charging data record (CDR) based on the offline charging information. The CDR is unrated at this point. The charging data function 110 transmits the unrated CDR to charging gateway function 112 via Ga interface 312. Charging gateway function 112 preprocesses the unrated CDR, such as for validation, consolidation, error-handling, etc, and filters the unrated CDR. Charging gateway function 112 also temporarily buffers the unrated CDR. Responsive to a request from billing system 106, charging gateway function 112 transmits the unrated CDR to billing system 106 via Bx interface 313. Billing system 106 includes an offline rating function 304 for determining the rate for offline charging of calls. Billing system 106 accesses the offline rating function 304 to determine a rate for the unrated CDR, and generates a rated CDR for the offline charging of the call session.
For online charging, online charging function 202 includes session-based charging function 204 and event based charging function 206 (see FIG. 2). Each function contains a charging data function to generate CDRs. An online charging function 202 (or its corresponding charging data function) receives online charging information from a charging trigger function 302 for a call session. Responsive to the online charging information, online charging function 202 accesses online rating function 210 to determine a rate for the call session associated with the online charging information. The online charging function 202 generates a rated CDR based on the rate for the call session and the online charging information, and transmits the rated CDR to charging gateway function 212 for CDR pre-processing via Ga interface 314. Charging gateway function 212 preprocesses the CDRs and filters the preprocessed CDRs. Charging gateway function 212 temporarily buffers the rated CDR. Responsive to a request from billing system 106, charging gateway function 112 transmits the rated CDR to billing system 106 via Bo interface 315.
One problem is that the existing 3GPP standard specifications do not describe a convergence between online charging and offline charging. The 3GPP only defines the specification that enables the charging gateway function 112 for the offline charging system 102 to feed an unrated CDR to the billing system 106 via Bx interface 313. The “x” of the Bx interface 313 may be a “c”, “p”, “i”, “l”, “m”, “o”, “w”, etc, depending on the network domain. For instance, “c” represents Circuit Switched (CS), “p” represents Packet Switched (PS), “i” represents IP Multimedia Subsystem (IMS), “l” represents Location Service, “m” represents Multimedia Message Service (MMS), “o” represents Online Charging System (OCS), and “w” represents Wireless LAN (WLAN). The billing system 106 thus needs its own independent offline rating function 304 in order to rate offline charges for calls. On the other hand, online charging system 104 includes its own online rating function 210 that rates online charging for calls.
The 3GPP does not define an interface to enable the charging gateway function 112 for the offline charging system 102 to feed CDRs to online charging system 104 for further rating and balance adjustment. Thus, most service operators need to manage, support, maintain, and update two separate charging systems from different vendors. The operational inefficiencies and technical overhead of maintaining two separate charging systems may lead to the service provider's drawback in marketing and business activities.